Role of Mg2+ and K+ Ions in Retention of Radio-Cesium (137cs+) in Vermiculite Clay

Radioactive cesium (137Cs+) is one of the most hazardous fission products in the radioactive liquid waste due to its large inventory, long half-life (t1/2 ∼30 years) and high environmental mobility. It is of vital importance to retain 137Cs+ within the waste repository boundary. Different clay minerals have shown great potential for scavenging metal ions from earth's critical zone. However, till date the molecular level retention mechanisms remain partly understood. Initial characterization of vermiculite clay was carried out by FTIR, SEM-EDX and PXRD. Adsorption of 137Cs+ from aqueous solution on vermiculite, under batch equilibrium experimental condition has been investigated. Different adsorption parameters were studied. Effect of Initial concentration of vermiculite doses was investigated. Adsorption experiment was carried out under different temperature and pH of the medium. Thermodynamical parameter of the adsorption process was evaluated. The effect of 137Cs+incorporation and solutions were analysed quantitatively using ICP-OES. 137Cs+ions loaded vermiculite clay was characterized by FTIR, SEM-EDX and PXRD to study the fate of the clay after adsorption. The retention of 137Cs+ ions inside vermiculite matrix was established by x-ray elemental mapping. It was confirmed that the Cs ions replaced the Mg ions from the crystal. The effect of 137Cs+adsorption on the structure of the clay minerals vermiculite in suspensions was elucidated. We proposed molecular level interaction of 137Cs+ions with the clay and described the mechanism of 137Cs+ions retention in clay.